[7.11] Line Strength Gradients in Spiral Bulges

B. K. Moorthy, J. A. Holtzman (New Mexico State University)

We present metallicity gradients in roughly a dozen spiral
bulges obtained with the Double Imaging Spectrograph at the
3.5m Apache Point Observatory telescope. The goal of the
project is to gain insight into the formation of central
bulges in spiral galaxies. Models for bulge formation
include dissipative collapse at the beginning of galaxy
formation, merger events over the lifetime of the galaxy,
and secular evolution with disk stars being inserted into
the bulge through bar instabilities. The collapse model
predicts strong metallicity gradients whereas secular
evolution predicts that bulges will look like disks with
minimal gradients. Mergers might cause any gradients to be
washed out. We comment on the implications of our results
for the different bulge formation models.

The author(s) of this abstract have provided an email address
for comments about the abstract:
bmoorthy@nmsu.edu